My year for this episode is estimated from the Stardate; it falls between 'The Return of the Archons' and 'A Taste of Armageddon'.

Plotline

The Enterprise is attacked by three Romulan vessels and hides in a gaseous energy field. After leaving the cloud, someone begins to play a series of practical jokes on the crew. The cloud has affected the ship's computer, causing the equivalent of a "nervous breakdown". Kirk must deal with the malfunctioning computer whilst simultaneously dealing with further Romulan attacks.